This invention relates to an improved process of forming noncyclic, aliphatic compounds having a multiplicity of primary amino groups in high yields and selectivity from corresponding polynitriles.
The hydrogenation of nitriles to amines using conventional hydrogenation catalysts is well known. However, it is recognized that this synthetic mode is not an effective process for forming noncyclic, aliphatic compounds from polynitriles having an atomic structure capable of forming cyclic or ring containing compounds.
The classic method for converting nitriles to amines has heretofore involved using hydrogenation catalysts in the form of finely-divided particles in a batch or slurry process. The batch reactor is by conventional design a fixed pressurized vessel in which all of the reactants are initially charged into the reaction vessel and all of the primary amine product is retained within the vessel until the process is terminated. As the nitrile is converted to imine intermediate, the imine tend to react with previously formed amine contained within the vessel as a by-product formation and thereby detract from the overall selectivity for the desired materials. Thus, when polynitriles are converted into polyamines using a conventional batch process, one conventionally obtains large amounts of cyclic product as well as methylated secondary amines and condensation by-products.
A further disadvantage of the batch process is the substantial capital equipment cost attributed to the large reactor size which is required to afford economic feasibility on an industrial scale and which is also necessary to accommodate the agitation equipment required in slurry reactors. Removal of the slurry catalyst also increases the downstream recovery costs in conventional batch processes.
Accordingly, it is desirable to find economically feasible and safe processes for forming, in high selectivity and yields, noncyclic aliphatic polyamines from the corresponding polynitriles. The desired linear polyamines have known usefulness as chelating and sequestering agents and as reagents in the formation and crosslinking of polymeric products, such as polyurethane and polyamines.
An object of this invention is to provide a process for the production of noncyclic, aliphatic amines in high yields and selectivity from the corresponding polynitriles.
It is also an object of the invention to provide an improved process for the hydrogenation of nitriles to noncyclic, aliphatic amines using nickel and chromium promoted Raney.RTM. cobalt catalyst under low pressure in a fixed bed, which process is more economical and efficient than conventional batch processes.
Other important objects of this invention will become apparent from the ensuing description and appended claims.